How Do Small Intestinal Bacteria Absorb Fat and Increase Obesity Risk?

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Highlights:

• Specific bacteria in the small intestine play a vital role in fat absorption
• Bacteria in the small intestine facilitate production and secretion of digestive enzymes that break down dietary fat increases the absorption of calorie-dense foods
• A high-fat diet can alter the microbial framework of the small intestine and pose a high risk for obesity

A new study focused on the microbes present in the upper gastrointestinal tract explains that the typical calorie-dense western diet can cause expansion of microbes that aid in the digestion and absorption of high-fat foods increasing the risk of obesity.

Role of Small Intestinal Bacteria in Fat Absorption
With response to consumption of high-fat foods, the bacteria present in the small bowel can multiply within 24 to 48 hours. The study findings suggest that these bacteria facilitate production and secretion of digestive enzymes into the small bowel.

‘Small intestinal bacteria help in the production and secretion of digestive enzymes into the small bowel which enable break down of dietary fat and increase the absorption of calorie-dense foods which leads to over-nutrition and obesity.’

The digestive enzymes produced by these microbes help in the break down of dietary fat and enable the rapid absorption of calorie-dense foods. The microbes also release bioactive compounds that stimulate the absorptive cells in the intestine to package and transport fat for absorption. On a long run, the presence of these microbes can lead to over-nutrition and obesity.

"These bacteria are part of an orchestrated series of events that make lipid absorption more efficient. Few people have focused on the microbiome of the small intestine, but this is where most vitamins and other micronutrients are digested and absorbed," said the senior author of the study, Eugene B. Chang, MD, the Martin Boyer Professor of Medicine and director of the NIH Digestive Diseases Research Core Center at the University of Chicago Medicine.

The study published in the journal Cell Host and Microbe is one of the first to show the specific role of small-bowel microbes in regulating both digestion and absorption of lipids which may have significant clinical applications in the prevention and treatment of obesity and cardiovascular disease, said Chang.

Goals of the Study

• To find out the role of microbes in digestion and absorption of fats
• To know the type of microbes involved
• To assess the role of diet-induced microbes on the digestion and uptake of fats

Details of the Study

The study involved mice that were germ-free, raised in isolated chambers and without any intestinal bacteria, and mice that were "specific pathogen free (SPF)," healthy but containing common non-disease causing microbes.

The germ-free mice provided with a high-fat diet were unable to digest or absorb fatty foods. There was no significant rise in the weight of the mice, but the lipid levels in their stools were found to be high.

In the case of SPF mice provided with a high-fat diet showed an increase in the weight. This diet increased the presence of certain microbes in the small intestine, such as microbes from the Clostridiaceae and Peptostreptococcaceae families. A member of Clostridiaceae was found to have a specific impact on absorption of fat. With a high-fat diet, the presence of other bacterial families such as Bifidobacteriacaea and Bacteriodacaea decreased and associated a decrease in weight.

Allowing certain microbes into the germ-free mice contributed to digestion of fat and also absorption of lipids.

Findings of the Study

The findings of the study show that a high-fat diet can alter the microbial framework of the small intestine. Dietary pressures such as calorie-dense foods can attract specific bacterial strains into the small intestine which help in the digestion and absorption of fats that can have a specific effect on extra-intestinal organs such as the pancreas, observed Chang.

The study is another step in developing ways to fight obesity. This can include an approach to decrease the abundance or activity of microbes that promote fat absorption or increasing the number of microbes that can prevent fat absorption.

"I would say the most important takeaway overall is the concept that what we eat--our diet on a daily basis--has a profound impact on the abundance and the type of bacteria we harbor in our gut," said Kristina Martinez-Guryn, PhD, lead author of the study, and now an assistant professor at Midwestern University in Downers Grove, IL. .

The presence of these microbes can affect the metabolism and ability to gain weight on specific diets.

The results of the study suggest that prebiotics or probiotics or developing new post-biotics (bacterial-derived compounds or metabolites) can be used to mainly enhance the nutrient uptake in people diagnosed with malabsorption disorders, such as Crohn's disease and obesity.

Reference:

1. Kristina Martinez-Guryn, Eugene B. Chang, et al. Small Intestine Microbiota Regulate Host Digestive and Absorptive Adaptive Responses to Dietary Lipids, Cell Host & Microbe (2018)DOI: 10.1016/j.chom.2018.03.011

Source: Medindia

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